RATIONALE: Biological therapies, such as denileukin diftitox, may be able to carry cancer-killing substances directly to cancer cells.

PURPOSE: This phase II trial is studying how well denileukin diftitox works in treating patients with T-cell leukemia/lymphoma.

OBJECTIVES:

Primary

• Determine the antitumor activity of denileukin diftitox, in terms of response rate, time to disease progression, and overall survival, in patients with Tac-expressing HTLV-1-associated adult T-cell leukemia/lymphoma.

Secondary

• Determine the safety of this drug in these patients.

OUTLINE: This is a non-randomized study.

Patients receive denileukin diftitox IV over 1 hour on days 1-5. Treatment repeats every 14 days for up to 24 courses in the absence of disease progression or unacceptable toxicity. Patients achieving a complete response (CR) receive 2 additional courses of treatment beyond CR.

After completion of study treatment, patients are followed at 4 weeks, every 1-3 months for 1 year, every 4 months for 1 year, every 6 months for 3 years, and then annually thereafter.

PROJECTED ACCRUAL: A total of 9-29 patients will be accrued for this study within 1-2½ years.

DISEASE CHARACTERISTICS:

• Histologically confirmed Tac-expressing adult T-cell leukemia/lymphoma (ATL)
• All stages allowed, including chronic, lymphomatous, or acute (ATL)
• HTLV-1 antibody positive
• More than 10% of malignant cells must express CD25
• Measurable disease, defined as > 10% abnormal (i.e., TAC homogenous strongly expressing) peripheral blood mononuclear cells
• No smoldering ATL
• No symptomatic leukemic meningitis* NOTE: *Patients with ATL and another HTLV-1-associated disease (i.e., tropical spastic paraparesis) are eligible

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Not specified

Life expectancy

• More than 2 months

Hematopoietic

• Granulocyte count ≥ 1,000/mm^3
• Platelet count ≥ 50,000/mm^3

Hepatic

• AST and ALT ≤ 2.5 times upper limit of normal (ULN)
• Bilirubin ≤ 3.0 mg/dL
• Albumin ≥ 2.5 g/dL

Renal

• Creatinine < 2.0 mg/dL

Cardiovascular

• No myocardial infarction within the past 6 months
• No severe coronary artery disease

Other

• Not pregnant
• No nursing during and for 3 months after completion of study treatment
• Negative pregnancy test
• Fertile patients must use effective contraception during and for 6 months after completion of study treatment
• No other serious illness
• HIV negative

PRIOR CONCURRENT THERAPY:

Biologic therapy

• No prior denileukin diftitox
• No concurrent monoclonal antibodies
• No concurrent gammaglobulin

Chemotherapy

• At least 3 weeks since prior cytotoxic chemotherapy for ATL
• No concurrent chemotherapy

Endocrine therapy

• Prior or concurrent corticosteroids allowed

Radiotherapy

• Not specified

Surgery

• Not specified

Other

• No concurrent drugs that would affect lymphocytes
• No other concurrent investigational anticancer drugs